A common type of optical cable includes a buffer tube which loosely surrounds an optical fiber, with the buffer tube usually, but not always, surrounded by a strength member and jacket. A common way to connect an end of the optical cable to a terminus, is to leave the optical fiber extending a few centimeters forward of the end of the buffer tube. A drop of adhesive is placed against the end of the buffer tube and optical fiber to seal the space between them and to prevent movement of the optical fiber within the buffer tube. The optical fiber and buffer tube are inserted into a terminus containing liquid epoxy, and the epoxy is hardened. The drop of adhesive previously applied to the end of the buffer tube, prevents the epoxy from wicking through the space between the optical fiber and buffer tube, and thereby causing damage to the optical cable as well as depleting the supply of epoxy for the termination.
The application of a dab of adhesive does not work well to reliably seal the front end of the buffer tube to the optical fiber. It is difficult to control the amount of adhesive and to symmetrically apply it, with too little or an asymmetrically applied adhesive resulting in a gap, and with too much or an asymmetrically applied adhesive possibly resulting in a large bulge which can prevent the forward portion of the buffer tube from seating in a portion of a terminus hole. If the adhesive has a high viscosity it may not seal, and if it has a low viscosity the adhesive may wick up the buffer tube. If the adhesive is not chosen well, it may have a thermal coefficient of expansion very different from that of the buffer tube and optical fiber, resulting in additional problems. Finally, the buffer tube is commonly formed of a TEFLON type (polytetrafluoroethylene) of material, which is difficult to adhere to. It might be possible to place a thin metal tube around the buffer and crimp it, but such crimping is not likely to provide a reliable seal, and may damage the optical cable. The buffer tube will not retain a crimp and will likely break if compressed a lot in diameter, unlike metal tubes. A method for sealing a forward end portion of a buffer tube to an optical fiber lying therewithin, which could be performed rapidly and reliably at low cost, would be of value in the termination of optical cables.